Oxidation catalysts comprising metal-complexes are well known. Such catalysts have been proposed for use in laundry compositions as components of a bleaching system. These catalysts activate H2O2 or other peroxygen sources.
A particular catalyst is disclosed in WO 98/03263, filed 21 Jul. 1997, (Collins et al.), which comprises a macrocyclic (tetra) amido N-donor. The macrocycle is capable of complexing with a metal ion, for example an iron III or IV. The complex also comprises axial ligands and one or more counter ions.
One proposed purpose of these catalysts has been to assist in the bleaching of dyestuffs released from articles being laundered. If these dyestuffs are not removed from the wash liquor then they will re-deposit onto articles and cause a loss of colour definition or even catastrophic damage to ‘white’ articles. U.S. Pat. No. 5,853,428, filed 24 Feb. 1997, (Collins et al.) discloses use of similar catalysts in laundry detergent compositions. In both these citations the addition of hydrogen peroxide, or a source thereof, is envisaged as a means of activating the catalyst.
Bleaching agents typically present in laundry detergents include percarbonates and/or perborates, which can also act as sources of hydrogen peroxide and/or other peroxyl species.
Bleaching catalysts capable of bleaching effectively in the absence of added peroxyl sources have recently become the focus of some interest, for example: WO9965905; WO0012667; WO0012808; WO0029537, and, WO0060045. It is believed that these catalysts have the capability to use atmospheric oxygen as a source of oxidising equivalents.